P1383: STRONG AND SELECTIVE EX VIVO EXPANSION OF ADAPTIVE NKG2C+/CD57+ NK CELLS FROM CMV SEROPOSITIVE DONORS USING DENDRITIC CELLS DERIVED FROM THE LEUKEMIC CELL LINE DCONE AS FEEDER CELLS.
Authors: Haoxiao Zuo, Hester van Zeeburg, Alex Karlsson-Parra, Satwinder Kaur Singh
Journal: HemaSphere (2023)

Topic: 24. Gene therapy, cellular immunotherapy and vaccination - Biology & Translational Research Background: Human cytomegalovirus (CMV) infection profoundly affects the NK cell compartment, as documented by the presence of a long-lived adaptive NK cell subset co-expressing NKG2C and CD57. Notably, expansion of adaptive NK cells after CMV reactivation in recipients of allogeneic hematopoietic cell transplantation (HCT) is associated with a lower rate of relapse of acute myeloid leukemia (Cichocki et al. 2016). Additionally, higher absolute numbers of adaptive NK cells after autologous HCT has been shown to be associated with significantly decreased risk of relapse in patients with multiple myeloma (Merino et al. 2020). The requirements for adaptive NK cell expansion ex vivo for subsequent adoptive cell therapy have however not been fully characterized. Aims: To explore if mature dendritic cells derived from the proprietary acute myeloid leukemia cell line DCOne, co-expressing DC-associated and tumor-associated ligands for activating NK cell receptors, could function as efficient feeder cells for ex vivo expansion of cytokine-stimulated adaptive NK cells from CMV-positive subjects. Methods: Healthy CMV seropositive blood donors were used as source for expansion of adaptive NK cells. PBMCs were separated from buffy coats by density gravity centrifugation and NK cells were enriched from PBMCs using negative bead-based isolation. Isolated NK cells were co-cultured with or without irradiated DCOne-derived mature DCs (high expression of HLA-DR, CD40/80/86 and CD83) in the presence of cytokines (IL-2, IL-15 or IL-2 and IL-15) for 2 weeks. After 1 week, cells were restimulated with fresh DCOne-derived mature DCs. NK cell expansion, viability and phenotype were monitored on day 7 and 14. Results: DCOne-derived mature DCs were found to highly express CD58 (ligand for the activating NK cell receptor CD2), and the DNAM-1 ligands CD155 and CD112. When used as feeder cells and co-cultured for 2 weeks with isolated NK cell from CMV-positive healthy donors, a selective (Figure 1) and strong (>200-fold) median expansion (Figure 2) of adaptive NKG2C+/CD57+ NK cells was found when cocultures were performed in medium supplemented with IL-2 and/or IL-15. Characterization of the functional profile, including ADCC, cytokine production and long-time survival, after target cell interaction by these expanded NK cells is ongoing. Summary/Conclusion: The presented data indicate that DCOne-derived mature DCs are endowed with the capability to promote strong and selective ex vivo expansion of adaptive NKG2C+/CD57+ NK cells from CMV+ subjects or donors. Such expanded NK cells could be used for adoptive immunotherapy, including combinations with tumor-targeting antibodies or NK cell engagers, in different hematological tumor indications, or as adoptive cell therapy post HSCT.Keywords: Cellular therapy, Immunotherapy, NK cell, Ex vivo expansion